The Experts below are selected from a list of 255 Experts worldwide ranked by ideXlab platform
Ellen R Graber - One of the best experts on this subject based on the ideXlab platform.
-
immobilization and deactivation of pathogenic enzymes and toxic metabolites by biochar a possible mechanism involved in soilborne disease suppression
Soil Biology & Biochemistry, 2018Co-Authors: Amit Kumar Jaiswal, Yigal Elad, Ellen R. Graber, Omer Frenkel, Ludmila Tsechansky, Yigal Elad, Ellen R GraberAbstract:Abstract Adding biochar to soil and Soilless Media can help protect plants against diseases caused by soilborne pathogens. There are a number of direct and indirect mechanisms that are potentially responsible for this effect. This study tested the hypothesis that biochar adsorption and consequent deactivation of cell wall degrading enzymes (CWDEs) and toxic metabolites produced by soilborne pathogens can help defend plant roots against pathogen attack. The specific objectives were to: (i) quantify adsorption and inactivation of model extracellular pathogenic enzymes (polygalacturonase and cellulase) by 4 model biochars; and (ii) determine the effect of biochar adsorption of CWDEs and toxic metabolites produced by Fusarium oxysporum f. sp. radicis lycopersici (FORL) on the severity of disease symptoms in tomato seedlings. All the enzyme adsorption isotherms were strongly non-linear and well-described by the Langmuir model. Maximum adsorption capacity (Qm) was generally greater for polygalacturonase than cellulase on a given biochar, and reached as high as 448 g polygalacturonase per kg biochar. There was no straightforward relationship between biochar adsorption capacity and its surface area or any other biochar characteristics. The adsorbed enzymes were 100% immobilized by the biochars, and the immobilized enzymes were revealed to be substantially deactivated. Activity of immobilized polygalacturonase ranged from 16 to 30% on the four biochars, and activity of immobilized cellulase ranged from 5 to 9%. There were no significant relationships between deactivation extent and any determined biochar physical and chemical characteristic or substrate/product adsorption characteristics. In the tomato seedling bioassay, the adsorption of FORL-produced enzymes and toxic metabolites led to substantially lessened disease-like symptom severity. Thus, the hypothesis was successfully confirmed. We anticipate that adsorption/deactivation of virulence factors by biochar is part of the puzzle responsible for biochar's varied impacts on severity of soilborne disease, but not the only part. This is because most biochar dose-disease resistance curves are non-monotonic, and reveal best results at some interim biochar dose. This would not be the case if only adsorption/deactivation was important, since in that event, increasing biochar dose would increasingly remove virulence factors from near the plant roots.
-
biochar impact on development and productivity of pepper and tomato grown in fertigated Soilless Media
Plant and Soil, 2010Co-Authors: Ellen R Graber, A Silber, Yael Meller Harel, Max Kolton, Eddie Cytryn, Dalia Rav David, Ludmilla Tsechansky, Menahem Borenshtein, Yigal EladAbstract:The impact of additions (1–5% by weight) of a nutrient-poor, wood-derived biochar on pepper (Capsicum annuum L.) and tomato (Lycopersicum esculentum Mill.) plant development and productivity in a coconut fiber:tuff growing mix under optimal fertigation conditions was examined. Pepper plant development in the biochar-treated pots was significantly enhanced as compared with the unamended controls. This was reflected by a system-wide increase in most measured plant parameters: leaf area, canopy dry weight, number of nodes, and yields of buds, flowers and fruit. In addition to the observed increases in plant growth and productivity, the rhizosphere of biochar-amended pepper plants had significantly greater abundances of culturable microbes belonging to prominent soil-associated groups. Phylogenetic characterization of unique bacterial isolates based on 16S rRNA gene analysis demonstrated that of the 20 unique identified isolates from roots and bulk soil from the char-amended growing mix, 16 were affiliated with previously described plant growth promoting and/or biocontrol agents. In tomato, biochar treatments positively enhanced plant height and leaf size, but had no effect on flower and fruit yield. The positive impacts of biochar on plant response were not due to direct or indirect effects on plant nutrition, as there were no differences between control and treatments in leaf nutrient content. Nor did biochar affect the field capacity of the Soilless mixture. A number of organic compounds belonging to various chemical classes, including n-alkanoic acids, hydroxy and acetoxy acids, benzoic acids, diols, triols, and phenols were identified in organic solvent extracts of the biochar. We conjecture two related alternatives to explain the improved plant performance under biochar treatment: (i) the biochar stimulated shifts in microbial populations towards beneficial plant growth promoting rhizobacteria or fungi, due to either chemical or physical attributes of the biochar; or (ii) low doses of biochar chemicals, many of which are phytotoxic or biocidal at high concentrations, stimulated plant growth at low doses (hormesis).
Bruce Bugbee - One of the best experts on this subject based on the ideXlab platform.
-
ceramic aggregate sorption and desorption chemistry implications for use as a component of Soilless Media
Journal of Plant Nutrition, 2014Co-Authors: Curtis B Adams, Astrid R Jacobson, Bruce BugbeeAbstract:Ceramic aggregates (Turface® and Profile®) are common Soilless Media components, but their sorption/desorption chemistry is poorly understood. We investigated: labile (readily desorb-able or readily plant-available) ion concentrations; the effect of rinsing and soaking pretreatments on labile ions; sorption of applied nutrients; and nutrient uptake from the aggregates by plants. Variability in labile ions was extremely high among bags of aggregates. Manganese, boron, magnesium, calcium, sulfur and potassium were most likely to desorb in excess for plants. Phosphorus, iron, copper and zinc were sorbed by the aggregates; only copper was found nearly deficient in plant tissue. Rinsing and soaking pretreatments adjusted labile ions to more suitable concentrations for plants. However, growth data suggested a worst-case scenario of high levels of labile ions may not be mitigated by these pretreatments. With frequent leaching after planting or where the aggregates are a minor component of Media, excessive nutrie...
-
macro and micronutrient release characteristics of three polymer coated fertilizers theory and measurements
Journal of Plant Nutrition and Soil Science, 2013Co-Authors: Curtis B Adams, Jonathan M Frantz, Bruce BugbeeAbstract:In spite of several published studies we have an incomplete understanding of the ion-release mechanisms and characteristics of polymer-coated fertilizers (PCF). Here we extend current conceptual models describing release mechanisms and describe the critical effects of substrate moisture and temperature on macro- and micronutrient release of three PCF types: Polyon ® , Nutricote ® , and Osmocote ® . Nutrient release was quantified at weekly intervals for up to 300 d from 5°C to 40°C in water and chemically inert sand, substrates that allowed release quantification without confounding effects of ion sorption/desorption. At least two release-timeframe formulations of each PCF type were studied and all products had similar nutrient concentrations to allow isolation of the effect of coating technology. Contrary to several studies, our data and model indicate that there is no significant difference in nutrient-release rates in water and a moist, solid substrate. This means that release rates determined in water can be used to model bio-available nutrient concentrations in moist soil or Soilless Media where sorption/desorption properties alter concentrations after release. Across all PCF, the nutrients most affected by temperature were typically N, K, B, Cu, and Zn, while the least affected were P, Mg, and Fe. We also found consistent differences among the coating technologies. Osmocote fertilizers released faster than specified at both high and low temperatures. Nutricote had relatively steady release rates over time and a nonlinear response to temperature. Polyon released more slowly than specified but replicate samples were highly uniform.
-
very high co2 reduces photosynthesis dark respiration and yield in wheat
Annals of Botany, 1997Co-Authors: Bruce Bugbee, Joseph ReuveniAbstract:Although terrestrial CO2 concentrations, [CO2] are not expected to reach 1000 micromoles mol-1 for many decades, CO2 levels in closed systems such as growth chambers and glasshouses, can easily exceed this concentration. CO2 levels in life support systems in space can exceed 10000 micromoles mol-1 (1%). Here we studied the effect of six CO2 concentrations, from ambient up to 10000 micromoles mol-1, on seed yield, growth and gas exchange of two wheat cultivars (USU-Apogee and Veery-l0). Elevating [CO2] from 350 to 1000 micromoles mol-1 increased seed yield (by 33%), vegetative biomass (by 25%) and number of heads m-2 (by 34%) of wheat plants. Elevation of [CO2] from 1000 to 10000 micromoles mol-1 decreased seed yield (by 37%), harvest index (by 14%), mass per seed (by 9%) and number of seeds per head (by 29%). This very high [CO2] had a negligible, non-significant effect on vegetative biomass, number of heads m-2 and seed mass per head. A sharp decrease in seed yield, harvest index and seeds per head occurred by elevating [CO2] from 1000 to 2600 micromoles mol-1. Further elevation of [CO2] from 2600 to 10000 micromoles mol-1 caused a further but smaller decrease. The effect of CO2 on both wheat cultivars was similar for all growth parameters. Similarly there were no differences in the response to high [CO2] between wheat grown hydroponically in growth chambers under fluorescent lights and those grown in Soilless Media in a glasshouse under sunlight and high pressure sodium lamps. There was no correlation between high [CO2] and ethylene production by flag leaves or by wheat heads. Therefore, the reduction in seed set in wheat plants is not Mediated by ethylene. The photosynthetic rate of whole wheat plants was 8% lower and dark respiration of the wheat heads 25% lower when exposed to 2600 micromoles mol-1 CO2 compared to ambient [CO2]. It is concluded that the reduction in the seed set can be mainly explained by the reduction in the dark respiration in wheat heads, when most of the respiration is functional and is needed for seed development.
Yigal Elad - One of the best experts on this subject based on the ideXlab platform.
-
immobilization and deactivation of pathogenic enzymes and toxic metabolites by biochar a possible mechanism involved in soilborne disease suppression
Soil Biology & Biochemistry, 2018Co-Authors: Amit Kumar Jaiswal, Yigal Elad, Ellen R. Graber, Omer Frenkel, Ludmila Tsechansky, Yigal Elad, Ellen R GraberAbstract:Abstract Adding biochar to soil and Soilless Media can help protect plants against diseases caused by soilborne pathogens. There are a number of direct and indirect mechanisms that are potentially responsible for this effect. This study tested the hypothesis that biochar adsorption and consequent deactivation of cell wall degrading enzymes (CWDEs) and toxic metabolites produced by soilborne pathogens can help defend plant roots against pathogen attack. The specific objectives were to: (i) quantify adsorption and inactivation of model extracellular pathogenic enzymes (polygalacturonase and cellulase) by 4 model biochars; and (ii) determine the effect of biochar adsorption of CWDEs and toxic metabolites produced by Fusarium oxysporum f. sp. radicis lycopersici (FORL) on the severity of disease symptoms in tomato seedlings. All the enzyme adsorption isotherms were strongly non-linear and well-described by the Langmuir model. Maximum adsorption capacity (Qm) was generally greater for polygalacturonase than cellulase on a given biochar, and reached as high as 448 g polygalacturonase per kg biochar. There was no straightforward relationship between biochar adsorption capacity and its surface area or any other biochar characteristics. The adsorbed enzymes were 100% immobilized by the biochars, and the immobilized enzymes were revealed to be substantially deactivated. Activity of immobilized polygalacturonase ranged from 16 to 30% on the four biochars, and activity of immobilized cellulase ranged from 5 to 9%. There were no significant relationships between deactivation extent and any determined biochar physical and chemical characteristic or substrate/product adsorption characteristics. In the tomato seedling bioassay, the adsorption of FORL-produced enzymes and toxic metabolites led to substantially lessened disease-like symptom severity. Thus, the hypothesis was successfully confirmed. We anticipate that adsorption/deactivation of virulence factors by biochar is part of the puzzle responsible for biochar's varied impacts on severity of soilborne disease, but not the only part. This is because most biochar dose-disease resistance curves are non-monotonic, and reveal best results at some interim biochar dose. This would not be the case if only adsorption/deactivation was important, since in that event, increasing biochar dose would increasingly remove virulence factors from near the plant roots.
-
biochar impact on development and productivity of pepper and tomato grown in fertigated Soilless Media
Plant and Soil, 2010Co-Authors: Ellen R Graber, A Silber, Yael Meller Harel, Max Kolton, Eddie Cytryn, Dalia Rav David, Ludmilla Tsechansky, Menahem Borenshtein, Yigal EladAbstract:The impact of additions (1–5% by weight) of a nutrient-poor, wood-derived biochar on pepper (Capsicum annuum L.) and tomato (Lycopersicum esculentum Mill.) plant development and productivity in a coconut fiber:tuff growing mix under optimal fertigation conditions was examined. Pepper plant development in the biochar-treated pots was significantly enhanced as compared with the unamended controls. This was reflected by a system-wide increase in most measured plant parameters: leaf area, canopy dry weight, number of nodes, and yields of buds, flowers and fruit. In addition to the observed increases in plant growth and productivity, the rhizosphere of biochar-amended pepper plants had significantly greater abundances of culturable microbes belonging to prominent soil-associated groups. Phylogenetic characterization of unique bacterial isolates based on 16S rRNA gene analysis demonstrated that of the 20 unique identified isolates from roots and bulk soil from the char-amended growing mix, 16 were affiliated with previously described plant growth promoting and/or biocontrol agents. In tomato, biochar treatments positively enhanced plant height and leaf size, but had no effect on flower and fruit yield. The positive impacts of biochar on plant response were not due to direct or indirect effects on plant nutrition, as there were no differences between control and treatments in leaf nutrient content. Nor did biochar affect the field capacity of the Soilless mixture. A number of organic compounds belonging to various chemical classes, including n-alkanoic acids, hydroxy and acetoxy acids, benzoic acids, diols, triols, and phenols were identified in organic solvent extracts of the biochar. We conjecture two related alternatives to explain the improved plant performance under biochar treatment: (i) the biochar stimulated shifts in microbial populations towards beneficial plant growth promoting rhizobacteria or fungi, due to either chemical or physical attributes of the biochar; or (ii) low doses of biochar chemicals, many of which are phytotoxic or biocidal at high concentrations, stimulated plant growth at low doses (hormesis).
Karl Piepho - One of the best experts on this subject based on the ideXlab platform.
-
undergraduate sustainable learning effects of sustainable Soilless Media on production and sensory evaluation of cucumbers basil parsley and lettuce
Sustainability, 2011Co-Authors: Neil O Anderson, Joey Annis, Mark Buchholz, Jared Cutting, Eric Heuring, Emily Jankila, Megan Mccrumb, Nicole Nelson, Myra Pehoski, Karl PiephoAbstract:Modern greenhouse production has been ~100% reliant on fossil fuels for all inputs (glazing, heating, fertilization, lighting, post-harvest). Recent innovations may reduce fossil fuel dependence but their effectiveness may not be thoroughly tested. To promote education in sustainable production, undergraduate students in Greenhouse Management class (Hort 3002W; University of Minnesota) tested the effectiveness of two organic or ‘sustainable’ Soilless Media (Sunshine Natural and Organic Growing Mix, Sungro Metro-Mix Special Blend) with a control (Sunshine LC8 Professional) for crop production (height, leaf/flower number, yield) and sensory evaluations (appearance, texture, taste, purchase) of cucumbers (‘Big Burpless Hybrid’, ‘Sweet Burpless Hybrid’), basil (‘Opal Purple’, ‘Redleaf’), parsley (‘Green River’, ‘Extra Curled Dwarf’, ‘Hamburg’), and lettuce (Flying Saucer ‘Green’, ‘Red’). Significant differences between sustainable vs. control soils occurred for plant growth, depending on vegetative or reproductive traits, crops, and cultivars. These differences occasionally disappeared for sensory evaluation of edible components. In most crops, however, cultivars were highly significant factors. Undergraduate research can be used to provide directionality for future vegetable and herb plant breeding to focus on creating cultivars with increased yield and high consumer acceptance when grown in sustainable greenhouse Soilless mixes.
A Silber - One of the best experts on this subject based on the ideXlab platform.
-
impact of short term acidification on nitrification and nitrifying bacterial community dynamics in Soilless cultivation Media
Applied and Environmental Microbiology, 2012Co-Authors: Eddie Cytryn, Irit Levkovitch, Yael Negreanu, Scot E Dowd, Sammy Frenk, A SilberAbstract:Soilless medium-based horticulture systems are highly prevalent due to their capacity to optimize growth of high-cash crops. However, these systems are highly dynamic and more sensitive to physiochemical and pH perturbations than traditional soil-based systems, especially during nitrification associated with ammonia-based fertilization. The objective of this study was to assess the impact of nitrification-generated acidification on ammonia oxidation rates and nitrifying bacterial community dynamics in Soilless growth Media. To achieve this goal, perlite Soilless growth medium from a commercial bell pepper greenhouse was incubated with ammonium in bench-scale microcosm experiments. Initial quantitative real-time PCR analysis indicated that betaproteobacterial ammonia oxidizers were significantly more abundant than ammonia-oxidizing archaea, and therefore, research focused on this group. Ammonia oxidation rates were highest between 0 and 9 days, when pH values dropped from 7.4 to 4.9. Pyrosequencing of betaproteobacterial ammonia-oxidizing amoA gene fragments indicated that r-strategist-like Nitrosomonas was the dominant ammonia-oxidizing bacterial genus during this period, seemingly due to the high ammonium concentration and optimal growth conditions in the Soilless Media. Reduction of pH to levels below 4.8 resulted in a significant decrease in both ammonia oxidation rates and the diversity of ammonia-oxidizing bacteria, with increased relative abundance of the r-strategist-like Nitrosospira. Nitrite oxidizers (Nitrospira and Nitrobacter) were on the whole more abundant and less sensitive to acidification than ammonia oxidizers. This study demonstrates that nitrification and nitrifying bacterial community dynamics in high-N-load intensive Soilless growth Media may be significantly different from those in in-terra agricultural systems.
-
biochar impact on development and productivity of pepper and tomato grown in fertigated Soilless Media
Plant and Soil, 2010Co-Authors: Ellen R Graber, A Silber, Yael Meller Harel, Max Kolton, Eddie Cytryn, Dalia Rav David, Ludmilla Tsechansky, Menahem Borenshtein, Yigal EladAbstract:The impact of additions (1–5% by weight) of a nutrient-poor, wood-derived biochar on pepper (Capsicum annuum L.) and tomato (Lycopersicum esculentum Mill.) plant development and productivity in a coconut fiber:tuff growing mix under optimal fertigation conditions was examined. Pepper plant development in the biochar-treated pots was significantly enhanced as compared with the unamended controls. This was reflected by a system-wide increase in most measured plant parameters: leaf area, canopy dry weight, number of nodes, and yields of buds, flowers and fruit. In addition to the observed increases in plant growth and productivity, the rhizosphere of biochar-amended pepper plants had significantly greater abundances of culturable microbes belonging to prominent soil-associated groups. Phylogenetic characterization of unique bacterial isolates based on 16S rRNA gene analysis demonstrated that of the 20 unique identified isolates from roots and bulk soil from the char-amended growing mix, 16 were affiliated with previously described plant growth promoting and/or biocontrol agents. In tomato, biochar treatments positively enhanced plant height and leaf size, but had no effect on flower and fruit yield. The positive impacts of biochar on plant response were not due to direct or indirect effects on plant nutrition, as there were no differences between control and treatments in leaf nutrient content. Nor did biochar affect the field capacity of the Soilless mixture. A number of organic compounds belonging to various chemical classes, including n-alkanoic acids, hydroxy and acetoxy acids, benzoic acids, diols, triols, and phenols were identified in organic solvent extracts of the biochar. We conjecture two related alternatives to explain the improved plant performance under biochar treatment: (i) the biochar stimulated shifts in microbial populations towards beneficial plant growth promoting rhizobacteria or fungi, due to either chemical or physical attributes of the biochar; or (ii) low doses of biochar chemicals, many of which are phytotoxic or biocidal at high concentrations, stimulated plant growth at low doses (hormesis).
-
chemical characteristics of Soilless Media
Soilless Culture#R##N#Theory and Practice, 2008Co-Authors: A SilberAbstract:This chapter deals with the chemical properties of Soilless Media. Tuff is a volcanic material used as a substrate for horticultural crops in Italy, Spain, France, Turkey, and Israel and had been the subject of considerable research with respect to chemical properties as a horticultural substrate. This chapter uses tuff as model for illustration and elucidation of the chemical processes taking place in Soilless Media systems. The first category of chemical property described is that related to charge characteristics. This includes cation exchange capacity, anion exchange capacity, and pH titration analysis. Following this, the study discusses specific adsorption and interactions between cations/anions and substrate solids. The solubility and the interactions of nutritional elements with the substrate solids are associated with ion characteristics such as valence, size, and hydration status. Furthermore, it deals with plant-induced changes in the rhizosphere. Under this, it considers the effects on chemical properties of surfaces of substrate solids. Plant growth may affect the chemical properties of the substrate solids through three main mechanisms: changes of the surface charge and chemical properties of the solids through the addition of specifically adsorbed ions, addition of new solid materials, and accumulation of root exudates and decomposition products. Finally, this chapter explains nutrient release from inorganic and organic substrates.